Charge order induced by electron-lattice interaction in NaV2O5

TL;DR

This study uses density matrix renormalization group calculations to show that electron-lattice interactions induce charge order in NaV2O5, aligning well with experimental observations and reducing the Coulomb repulsion needed for charge ordering.

Contribution

It demonstrates that electron-lattice coupling significantly influences charge order formation and reduces the critical Coulomb repulsion in NaV2O5, providing a detailed theoretical analysis with experimental relevance.

Findings

Charge order appears with lattice distortions matching experiments.

Electron-lattice interaction lowers the Coulomb repulsion threshold for charge order.

Results at V=0.46 eV agree with experimental data.

Abstract

We present Density Matrix Renormalization Group calculations of the ground-state properties of quarter-filled ladders including static electron-lattice coupling. Isolated ladders and two coupled ladders are considered, with model parameters obtained from band-structure calculations for $\alpha^\prime$-NaV$_2$O$_5$. The relevant Holstein coupling to the lattice causes static out-of-plane lattice distortions, which appear concurrently with a charge-ordered state and which exhibit the same zigzag pattern observed in experiments. The inclusion of electron-lattice coupling drastically reduces the critical nearest-neighbor Coulomb repulsion $V_c$ needed to obtain the charge-ordered state. No spin gap is present in the ordered phase. The charge ordering is driven by the Coulomb repulsion and the electron-lattice interaction. With electron-lattice interaction, coupling two ladders has virtually no effect on $V_c$ or on the characteristics of the charge-ordered phase. At $V=0.46\eV$, a value consistent with previous estimates, the lattice distortion, charge gap, charge order parameter, and the effective spin coupling are in good agreement with experimental data for NaV$_2$O_5$.